Equipment is now in widespread use which is designed to automatically pluck fibers from a plurality of fiber bales and then deliver such fibers to a hopper or an apron in a fiber processing system. Equipment of this type is disclosed in U.S. Pat. No. 3,777,908 and in U.S. application Ser. No. 598,434, filed July 23, 1975, now U.S. Pat. No. 3,986,623, and such equipment has been found to have particular application in bale opener systems where different kinds of fibers are opened and mixed or blended in a predetermined ratio.
In systems of this sort, one or more hoppers are used, and each hopper has a plurality of bales located adjacent thereto in a bale laydown, with some of the bales in the laydown normally having a fiber content different from other bales in the laydown whereby a predetermined blend will be obtained when fiber is plucked from all of the bales in a laydown and delivered to the hopper. Each hopper continuously opens the fiber clumps fed thereto and delivers such opened fiber to a blending line, and each hopper normally includes an apron or conveyor extending from the intake side thereof to receive and collect the fibers plucked from the bales and then automatically convey such fibers to the hopper in response to a signal from the hopper indicating that it requires an additional quantity of fiber.
The aforementioned equipment for automatically plucking and delivering fibers to the hopper apron includes an elevated trackway on which a pick-up head is carried, and an automatic control system is provided for causing the pick-up head to move across the line of hopper aprons and monitor such aprons to determine which of them are empty and require additional fibers. If an apron is empty (e.g., it has automatically fed the fibers previously supplied thereto to the hopper), a signal is generated by a photoelectric cell in such apron that is detected by the pick-up head monitoring system, and the pick-up head is then caused to move, serially, to a position above each bale located adjacent such apron, pluck an increment of fiber therefrom, and deliver such increment to the apron, all as explained in greater detail in the aforesaid U.S. application Ser. No. 598,434. Thus, when an apron signals that it is empty, one increment of fiber is automatically plucked from each bale adjacent the apron and delivered to the apron in sequence, whereby the apron is always supplied with the desired proportions of fibers from all of the bales in the bale laydown, and this quantity of fibers accumulates on the apron until the hopper automatically causes the apron to feed such accumulated fibers to the hopper as described above.
In some situations, particularly when it is desirable to feed fibers from a large number of bales to a single hopper, a relatively large quantity of fiber may accumulate on the apron at one time because the pick-up head will automatically deliver in crements of fiber thereto from all of these bales, and all of the increments of fiber will be delivered to the apron before the hopper signals for additional fiber. Moreover, when the hopper does thereafter signal for additional fiber, the apron will deliver all of this large accumulation to the hopper at one time, and this will frequently cause the hopper to choke. More specifically, the hopper, as indicated above, generates a signal for additional fiber when the fiber therein reaches a predetermined minimum level, but this predetermined minimum level, when combined with the large accumulation of fiber fed thereto by the apron, will often result in the fiber exceeding a predetermined maximum level so as to cause the hopper to become choked.
Thus, if a hopper has a predetermined maximum fiber level of 100 pounds and a predetermined minimum level of 40 pounds, and if the pick-up head is programmed to deliver fiber to the apron from four bales in increments of 20 pounds from each bale, it will be apparent that 80 pounds of fiber could accumulate on the apron so that when this 80 pounds is fed to the hopper and combined with the 40 pounds already therein, the 120 pounds of fiber could choke the hopper.
In an effort to overcome this choking problem, an attempt was made to utilize a time delay circuit between the aforesaid photoelectric cell in the apron and the drive therefor whereby when the first increment of fiber was delivered to the apron, the photoelectric cell circuit would close to cause the apron to be driven for a predetermined length of time to deliver the first increment of the fiber to the hopper, even though it was not signaling for additional fiber, and thereby decrease the accumulation of fiber on the apron. This predetermined length of time was selected to correspond of the time normally required for the pick-up head to go to the next bale and deliver the next increment to the apron. However, it has found that the time required for the pick-up head to travel to, and pluck from, different bales varied substantially, particularly where the bales being plucked were of varying heights, and this timed method of controlling the apron delivery was therefore not fully satisfactory in the field.
In accordance with the present invention, apparatus is provided for preventing choking of the hopper by controlling the apron in response to a predetermined number of fiber increments being delivered to the apron whereby the quantity of fiber delivered to the hopper by the apron can be effectively maintained at a level which will not choke the hopper.